Possible Lambeosaurine in the Hell Creek Formation

[Troodon]

Nothing new but this was presented at the SVP conference late in 2020 and could be of interest to some.  Nothing has been published the and all based on one isolated humerus.  Additional discoveries are most likely needed to demonstrate they were in that fauna.

 

A POSSIBLE LAMBEOSAURINE (HADROSAURIDAE: DINOSAURIA) HUMERUS FROM THE LATE MAASTRICHTIAN HELL CREEK FORMATION OF SOUTH DAKOTA Rolleri, L., Gates, Terry A., Zanno, Lindsay E. North Carolina Museum of Natural Sciences, Raleigh, North Carolina, U.S.A. Both hadrosaurine and lambeosaurine hadrosaurs were common components of Campanian faunas in North America. However, to date, only hadrosaurines (e.g., Edmontosaurus annectens) are definitely known to have survived into the late Maastrichtian on the continent. This is in contrast to the European and Asian record, where lambeosaurine species have been described from Maastrichtian formations (e.g., Amurosaurus, Charonosaurus, Blasisaurus), some of which are hypothesized to be closely related to North American species from the Campanian. Intriguing evidence of a lambeosaurine from the widely prospected Hell Creek Formation (late Maastrichtian) was presented nearly two decades ago, but these data have not yet been published. Here we describe a large, isolated humerus (NCSM 21814, North Carolina Museum of Natural Sciences) discovered in 1998 in Harding County, South Dakota, that may provide additional evidence on this topic. NCMNS 21814 is robust, bearing a pronounced, triangular deltopectoral crest (DPC). The general proportions of this specimen do not compare well with Edmontosaurus, the only currently accepted hadrosaurid from the formation, and some aspects, particularly a robust well-developed DPC, resemble the morphology of lambeosaurines. In order to more accurately compare NCSM 21814 to other hadrosaurids, we utilized several sources of previously published humeral measurements. In the ratio of DPC length to humeral length, NCSM 21814 is most similar to saurolophine taxa such as Edmontosaurus. However, using morphometrics that include the breadth of the DPC as a variable, NCSM 21814 aligns with lambeosaurines. In addition, the shape of the DPC of NCSM is unusual, in being more triangular than quadrilateral. This morphology may represent an extreme for Edmontosaurus, or may be a feature of a new taxon. Regardless, the discovery of a morphologically atypical hadrosaurid humerus in the otherwise widely sampled Hell Creek Formation, demonstrates higher morphological disparity than © 2020 BY THE SOCIETY OF VERTEBRATE PALEONTOLOGY 285 currently appreciated amongst hadrosaurids within one of the best studied Late Cretaceous ecosystems. 

[hadrosauridae]